Darwoodious great pics and now I can see how much time you have spent on this. If there was an award for better engineering of factory Italian engineering you would be in the finals (no bottle of vino for you at lunchtime!). Also helps to have a rotary and a striped X for this work. Is your heater pipe an exact copy of the bend and height as the original pipe was in the front? Dr. Jeff after seeing these pics the idea of piggy backing the heater pipes looks very doable especially if the inner/upper pipe has a slightly tighter radius to the lower heater pipe where they enter the oval hole! I feel deleting the drain plugs is a good idea.